Monolithic beam combined DFB quantum cascade laser arrays with integrated arrayed waveguide gratings

Quantum cascade lasers (QCLs) serve as compact mid-infrared sources, well suited for applications including trace chemical detection and free-space communications. Our study features the first generation of open-loop arrayed waveguide grating (AWG)-integrated QCL arrays. In this configuration, wavelength locking is performed by the DFB gratings for each array element while the AWG executes wavelength beam combining (WBC). The laser elements are designed in a master oscillator power amplifier (MOPA) configuration to boost signal strength. The chip combines 5 lasers operating near 4.65 µm wavelength in pulsed mode. The peak power of the best QCL element reached 1 W with a 2 kA/cm² threshold current density. After depositing an anti-reflection coating on the common output waveguide, the peak power increased to 3 W. These results showcase the feasibility of aligning the DFB wavelengths with AWG channel wavelengths to enable on-chip WBC of single-mode QCLs.